Vancouver, BC — Tekmira Pharmaceuticals Corporation (TSX: TKM), a leading developer of RNA interference (RNAi) therapeutics, announced today that the United States Patent & Trademark Office (USPTO) has issued three key patents covering portions of Tekmira’s technology. The patents protect aspects of Tekmira’s leading lipid nanoparticle technology (LNP), which are used to deliver nucleic acid drugs, including small interfering RNA (siRNA).

Dr. Mark J. Murray, Tekmira’s President and CEO, said, "Tekmira’s LNP formulations are the gold standard for siRNA delivery and the issuance of these patents is a key step in the successful commercialization of this technology by Tekmira and our partners. We have been investing in LNP technology for a decade and have established a solid foundation of intellectual property and a leading position in the field of nucleic acid drug development."

"These new patents cover key components of our LNP technology, which is already well validated in preclinical studies and is currently part of multiple clinical development programs sponsored by Tekmira and Tekmira’s partners. We continue to build on this research with the aim of strengthening our RNAi drug development platform and that of our partners using LNP technology, the most widely used in the industry," added Dr. Murray.

Specifically, the USPTO has issued claims in three patents covering LNP formulations and lipid components used in Tekmira’s LNP formulations. This includes two issued patents covering the cationic lipid DLinDMA and related cationic lipid analogues (U.S. Patent No. 7,745,651) as well as LNP formulations containing these novel cationic lipids (U.S. Patent No. 7,799,565). DLinDMA and a family of cationic lipids derived from DLinDMA are key components of Tekmira’s LNP technology and are used in current LNP formulations in clinical development. This intellectual property is based on research by Tekmira scientists on the role of cationic lipids in the systemic delivery of RNAi therapeutics as published in Heyes et al., J. Control Release, 107(2):276-87.

The third issued patent covers a class of lipid conjugates, PEG-C-DAAs (U.S. Patent No. 7,803,397). PEG-C-DAAs are another critical component of Tekmira’s LNP technology that are important in the manufacturing and stability of LNP formulations and the performance of the formulations in vivo. These conjugates are also used in current LNP formulations in clinical development.

About RNAi and Tekmira’s LNP Technology
RNAi therapeutics have the potential to treat a broad number of human diseases by "silencing" disease causing genes. The discoverers of RNAi, a gene silencing mechanism used by all cells, were awarded the 2006 Nobel Prize for Physiology or Medicine. RNAi therapeutics, such as "siRNAs," require delivery technology to be effective systemically. LNP technology is one of the most widely used siRNA delivery approaches for systemic administration. Tekmira’s LNP technology (formerly referred to as stable nucleic acid-lipid particles or SNALP) encapsulates siRNAs with high efficiency in uniform lipid nanoparticles which are effective in delivering RNAi therapeutics to disease sites in numerous preclinical models. Tekmira’s LNP formulations are manufactured by a proprietary method which is robust, scalable and highly reproducible and LNP-based products have been reviewed by multiple FDA divisions for use in clinical trials. LNP formulations comprise several lipid components that can be adjusted to suit the specific application.

About Tekmira
Tekmira Pharmaceuticals Corporation is a biopharmaceutical company focused on advancing novel RNAi therapeutics and providing its leading lipid nanoparticle delivery technology to pharmaceutical partners. Tekmira has been working in the field of nucleic acid delivery for over a decade and has broad intellectual property covering LNPs. Further information about Tekmira can be found at www.tekmirapharm.com. Tekmira is based in Vancouver, B.C.

Forward-looking Statements and Information
This press release contains "forward-looking statements" or "forward-looking information" within the meaning of applicable securities laws (collectively, "forward-looking statements"). Forward-looking statements are generally identifiable by use of the words "believes," "may," "plans," "will," "anticipates," "intends," "budgets", "could", "estimates", "expects", "forecasts", "projects" and similar expressions, and the negative of such expressions. Forward-looking statements in this news release include statements about Tekmira’s strategy, future operations, clinical trials, prospects and the plans of management; RNAi (ribonucleic acid interference) product development programs; use of lipid nanoparticle (LNP) technology by Tekmira’s licensees; and Tekmira’s expectations with respect to existing and future agreements with third parties.

With respect to the forward-looking statements contained in this news release, Tekmira has made numerous assumptions regarding, among other things: LNP’s status as a leading RNAi delivery technology; FDA approval with respect to commencing clinical trials; the use of LNP technology by Tekmira’s development partners and licensees; Tekmira’s ability to protect its intellectual property rights and not to infringe on the intellectual property rights of others; and the ability to succeed at establishing a successful commercialization program for any of Tekmira’s products. While Tekmira considers these assumptions to be reasonable, these assumptions are inherently subject to significant business, economic, competitive, market and social uncertainties and contingencies.

Additionally, there are known and unknown risk factors which could cause Tekmira’s actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements contained herein. Known risk factors include, among others: the possibility that other organizations have made advancements in RNAi delivery technology that Tekmira is not aware of; anticipated payments under contracts with Tekmira’s collaborative partners will not be received by Tekmira on a timely basis, or at all, or in the quantum expected by Tekmira; Tekmira’s ability to obtain and protect intellectual property rights, and operate without infringing on the intellectual property rights of others; Tekmira’s development partners and licensees conducting clinical trial and development programs will not result in expected results on a timely basis, or at all; and Tekmira may become subject to product liability or other legal claims for which the Company has made no accrual in its financial statements.

A more complete discussion of the risks and uncertainties facing Tekmira appears in Tekmira’s Annual Information Form dated March 31, 2010 available at www.sedar.com. All forward-looking statements herein are qualified in their entirety by this cautionary statement, and Tekmira disclaims any obligation to revise or update any such forward-looking statements or to publicly announce the result of any revisions to any of the forward-looking statements contained herein to reflect future results, events or developments, except as required by law.

Contact Information

Investors
Adam Peeler
The Equicom Group
Phone: 416-815-0700 x 225
Email: apeeler@equicomgroup.com

Ian Mortimer
Executive Vice President and Chief Financial Officer
Phone: 604-419-3200

Media
David Ryan
Longview Communications Inc.
Phone: 604-694-6031
Email: dryan@longviewcomms.ca